President Obama had similar questions after the Sandy Hook school shooting in Newton, Connecticut.

"Congress will fund research into the effects that violent video games have on young minds," he said at the time, also calling for policies that would ban the purchase of military-style weapons and improve background checks for firearm purchases (changes that could have an impact on gun violence).

For all of these reasons, people have lots of questions surrounding what science says about the effects of video games. Do games cause violence or aggression? Are they addictive? Are they healthy ways to relax and de-stress? Could they improve brain processing speed?

Similar questions have arisen after every new form of media appeared — including television, movies, pop music, comics, and even books.

Fortunately, there's a fair amount of research that about how video games affect our brains and bodies. Here are the most important takeaways.

Many kids and adults play video games — they're not just of interest to young men.

65% of households have at least one member who plays games three hours a week or more, and the average gamer is 35 years old.

Of the "gaming" population, there are more adult women (31%) than boys under 18 (18%).

Of people who play video games, 59% are male and 41% are female.

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Some studies link playing violent games to slight increases in aggression — though aggression is not the same as violence.

Warner Bros. Interactive

One review of research by the American Psychological Association found that people who played violent video games were very slightly more likely to engage in aggressive behavior (actions like playing a loud sound that people they were competing against could hear over an audio system). However, the APA said playing games was not enough to cause aggression.

The release of games like Grand Theft Auto doesn't seem to increase crime rates — and may do the opposite.

A 2015 study found that in the months after popular violent video games are released, aggravated assault and homicide rates tend to drop. The researchers behind the study said the explanations for this correlation are complicated. Some scientists think people might experience some aggression-reducing catharsis from playing violent games; others say that aggressive people might seek out violent media and then play games instead of engaging in behavior that might lead to criminal activity.

Either way, there doesn't seem to be any increase in criminal activity associated with playing games.

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Many of the people involved in mass shooting incidents seem to be less interested in violent video games than their peers.

A 2004 report on school shooters by the US Secret Service and Department of Education found that only 12% of school shooters displayed an interest in violent video games.

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In the time period that violent video games have become popular, youth violence has declined.

id Software / Bethesda Softworks

It's easy to find video games that depict blood, gore, and violence — which did not exist a few decades ago. Yet studies show that youth violence has consistently declined as these games have become available.

This is just a correlation — it does not mean that games cause violence rates to drop. But it also doesn't support the idea that violent games are "creating monsters," as Trump put it in 2012.

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Video games can't explain the US's outlier status in terms of gun violence.

REUTERS/Ina Fassbender

Various political figures have blamed school shootings on kids playing violent video games. Kentucky Governor Matt Bevin said guns were not a problem but that games desensitized players to the value of human life. NRA President Wayne LaPierre said after the Sandy Hook shooting that "Guns don't kill people. Video games, the media, and Obama's budget kill people."

But a comparison of the 10 largest video game markets in the world shows that there are far more gun murders in the US than in other countries that spend a lot of money on video games. That's even true in countries that spend more on games per capita than the US does, including Germany, Australia, the UK, Canada, France, Japan, and South Korea.

Specifically, the draft's language states that gaming behavior could be a disorder if it meets three characteristics: if a person loses control over their gaming habits, if they start to prioritize gaming over many other interests or activities, and if they continue playing despite clear negative consequences.

This would put gaming on a similar level as other behaviors that can become problematic if people lose control over them, though the concept of behavioral addiction is controversial in the first place.

Some researchers are uncertain about calling gaming "addictive," though. They argue that problematic gaming may instead serve as a dysfunctional coping mechanism for people struggling with depression or anxiety.

Researchers have found that video-game players can outperform non-gamers on visual tasks, and several studies have shown that video games can "train" visual processing skills in ways that translate to other activities.

In some studies, gamers show an increased ability to pay attention while filtering out distractions

The players were less distracted by other visual information than non-gamers in several studies the researchers analyzed. The same abilities weren't necessarily found in gamers who played other types of games, though.

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It's not just vision — action games seem to boost hand eye-coordination for adults and kids

Nintendo

Researchers studying the effects of gaming have asked gamers and non-gamers to complete a new motor-skills task that they hadn't seen before. They found that neither group was necessarily better than the other at the start, and both groups improved at the task over time. But the group that played video games became significantly more accurate by the end of the experiment.

Another small study found that young children who played video games had improved motor skills compared to their peers, though the researchers weren't certain whether these kids were simply more drawn to these games in the first place because of that skill.

Studies show that the more time kids (and adults) spend in front of screens playing games or watching TV, the more likely they are to be overweight or obese.

Reuters/Axel Schmidt

A number of studies show that the more time kids spend engaged in sedentary behavior, the more likely they are to be overweight. One study of German children found that kids who spent less than 1.5 hours a day in front of a TV were 75% less likely to be overweight than kids who spent more than 1.5 hours in front of a screen.

It's worth noting, however, that other studies have shown that socioeconomic and demographic factors have a bigger impact on childhood obesity than game playing.

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Kids who play sports video games are more likely to play sports.

EA Sports

Researchers who tracked Canadian high schoolers found that kids who played sports video games were more involved in sports. When kids started playing those games, they also became more likely to play real-life sports more in the future.

The researchers think that the games provided knowledge of the sport, which gave the children confidence that helped them get more involved in real life.

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Researchers think video games could improve problem-solving capacity

Firaxis/2K Games/Take-Two Interactive

Since many games include some puzzle-solving requirements, researchers have speculated that games could improve problem-solving skills and change the way people learn.

In one study of "World of Warcraft" players, researchers found improved problem-solving capacity, but they weren't sure whether the game made people better at solving problems or whether those people were drawn to the game in the first place.

There are also links between video-game playing and creativity.

Nintendo

Some researchers have found that kids who played video games were more creative than kids who didn't play — and it didn't matter which type of video game was used.

The same thing was not true for other technology use, like use of cell phones or the internet. But again, researchers aren't sure whether games made kids more creative or creative kids were drawn to games.

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Playing games can help people relax, feel better, and trigger positive emotional responses.

According to research from the American Psychological Association, games can elicit a range of emotions, positive and negative — including satisfaction, relaxation, frustration, and anger. Experiencing these emotions in a gaming context may help people regulate emotions, learn to cope with situations, and challenge themselves, the APA said.

Researchers have used video game technologies like virtual reality to help people recover from PTSD, get over phobias, and learn to manage drug addiction.

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Virtual-reality environments provide safe but real-feeling scenarios in which people can face fears and difficult situations with the support of a therapist. New technology is making these sorts of interventions much more accessible than they used to be.

The psychological effects of video games might vary depending on how much you play.

Nintendo

One study of 10- to 15-year old children found that kids who played less than an hour of video games a day were more satisfied than kids who didn't play games or kids who played one to three hours per day.

The groups of kids that didn't play or played between one and three hours daily seemed to have the same level life satisfaction. Kids who played more than three hours a day were less satisfied than any of the other groups.

From what we know, there are ways that video games can help people relax, challenge themselves, and even push their cognitive abilities. At the same time, it's quite possible that excessive time spent playing games — as with any hobby — may be unhealthy or a sign that someone is struggling.

But in general, video games seem to be just another form of entertainment.